1. Field of the Invention
The present invention relates to disk cartridges for storing electronic information, and more particularly, to a disk cartridge having a spun fabric liner.
2. Description of the Prior Art
Removable disk cartridges for storing digital electronic information typically comprise an outer casing or shell that houses a magnetic, magneto-optical or optical disk upon which electronic information can be stored. The cartridge shell often comprises upper and lower halves that are joined together to house the disk. The disk is mounted on a hub that rotates freely within the cartridge. When the cartridge is inserted into a disk drive, a spindle motor in the drive engages with the disk hub in order to rotate the disk within the cartridge at a given speed. The outer shell of the cartridge typically has an aperture near one edge to provide the recording heads of the drive with access to the disk. A shutter or door mechanism is often provided to cover the aperture when the cartridge is not in use to prevent dust or other contaminants from entering the cartridge and settling on the recording surface of the disk.
Although the cartridge shell and shutter mechanism provide some protection against contaminants entering the cartridge, some contaminants will inevitably reach the recording surface of the disk. For example, dust, smoke and other debris may enter the cartridge through the disk hub or through the cartridge shutter when the disk is inserted in a disk drive. Additionally, magnetic particles may be generated during manufacturing of the disk cartridge as well as during read/write operations in the disk drive. These contaminants can interfere with a read/write head causing errors and a potential loss of information.
To reduce the risk of read/write errors resulting from particles on the disk surface, cartridges often include one or more fabric liners within the cartridge placed in contact with the disk surface. These liners typically are formed of a mixture of non-woven fibers bonded together either thermally, with an adhesive binder, or through a hydroentangling process such as that described in U.S. Pat. No. 5,311,389.
As illustrated in U.S. Pat. Nos. 4,750,075, 5,006,948, 5,083,231 and 5,216,566, the fabric liners are typically affixed to the upper and lower halves of the cartridge shell between so that they lie in a plane above the respective surfaces of the disk. In each of these examples, lifters and opposing ribs are provided on the inner surfaces of the upper and lower shells to bring the fabric liners into contact with at least a portion of the disk surface. Essentially, the lifters and ribs cooperate to force the liners against the disk surface. While the use of lifters and/or ribs ensures that the fabric liner contacts the disk surface and wipes unwanted particles from the disk, the force with which the liners are pressed against the disk creates a significant amount of drag on the disk as it rotates within the cartridge. Increased drag requires a corresponding increase in the strength of the disk drive spindle motor. Additionally, the increased contact pressure between the liners and the disk increases wear on the disk surface.
As flexible media products have evolved the thickness of the magnetic recording layer has become progressively thinner. For example, the 1.44 MB floppy disk has a magnetic coating layer of about 2 microns thick. The 100 MB Zip.TM. disk has a magnetic coating layer which is about 0.4 microns thick, while the present generation Zip.TM. 250 disk has a thickness of about 0.24 microns. The Zip.TM. 250 disk is shown, for example, in application Ser. No. 09/161,007, filed Sep. 25, 1998.
Future generation flexible products are intended to have a magnetic coating thickness of about 0.15 microns or less. It can be seen from this progression of thinner and thinner magnetic coating layers that the task of wiping the media free of air suspended debris while at the same time not damaging the ever thinner magnetic coating is quite challenging.
Historically, non-woven fabrics made of cotton, polyester, rayon, nylon, polypropylene, cellulose and other low cost fibers have been used to wipe the surfaces of flexible media. In a typical floppy disk application, the liner is brought into contact with the flexible media surface through means of a lifter. Other methods include a fuzzed liner region where upstanding fibers were generated during the cartridge manufacturing process to contact the media surface. The ideal wiper is aggressive with its debris wiping action while at the same time being gentle in its physical interaction with the underlying thin magnetic coating. The fibers must not break easily and become a source of debris themselves. Also, a fiber which minimizes the wicking up of the media's lubricant in the process of wiping is of significant importance.
Accordingly, there is a need for a removable disk cartridge having a liner that provides adequate wiping of the disk to remove unwanted particles, that creates much less drag on the disk and does not damage the magnetic coating. The liner should also be low cost and easy to manufacture. The present invention satisfies these needs.